Best microcontroller for me to use?

Hey guys, Cycloned here. I am just hoping to start with Robotics. I know nothing, I have an NXT kit and have done some work with that, but nothing at a higher level, and now that Im in engineering I understand I've got to stop using such kits and actually start building robots from parts. I would like to know what microcontroller that I should use. There are some events in my college (robo wars, robo soccer, sumo wars, and an obstacle course) that I wish to participate, so I was wondering what would be well suited for such competitons.

I understand that since Im a beginner, I should probably use an augmented controller, so please do recommend one, and other things I might need to get started. I am going to be reading other articles on this forum, and I would appreciate being linked to guides, tuts, videos, etc so I can learn as much as possible.